1. Field of the Invention
The invention relates in general to electrical apparatus, and, more particularly, to circuit breakers having thermal and magnetic trip means.
2. Description of the Prior Art
Circuit breakers are widely used in commercial, industrial, and residential applications to provide on-off switching control of electrical apparatus and to provide protection to such apparatus by automatically interrupting the flow of current to the apparatus upon overcurrent conditions. Many circuit breakers provide rapid interruption of short-circuit conditions and delayed interruption of slight overload conditions by employing magnetic and thermal trip mechanisms. Magnetic trip mechanisms use current flow through the separable contacts of the circuit breaker to produce a magnetic field which attracts an armature, thereby releasing a latch and automatically opening the contacts. Thermal mechanisms route the circuit breaker breaker flow through a bimetal member so that an overcurrent flowing through the bimetal member will generate heat and cause the bimetal member to deflect, thereby releasing a latch and automatically opening the circuit breaker. It is desirable to provide thermal and magnetic trip assemblies which are more sensitive to current flow therethrough, thereby providing an increased measure of protection.
While circuit breakers provide convenience and protection in the control of electrical apparatus, their size and cost has made it impractical to include them in many installations. It is desirable to provide a circuit breaker of lower cost and more compact construction to allow the use of such a circuit breaker in a wider variety of applications.